Multi-stage carburetor



May 39 1966 R. M. sAxBY MULTI-STAGE CARBURETOR Filed OCT..

2 Sheets-Sheet 1 INVENTOR. /C// M S34/V57 A 7 7'0 /VEY MULTI-STAGE CARBURETOR "Filed Oct. l, 1962 2 Sheets-Sheet 2 ATTUR/VEY United States Patent O 3,249,099 MULTI-STAGE CARBURETOR Richard M. Saxby, Detroit, Mich., assigner to Holley Carburetor Company, Warren, Mich., a corporation of Michigan Filed Oct. 1, 1962, Ser. No. 227,275 2 Claims. (Cl. 123-103) This invention relates to carburetors for internal combustion engines, and more particularly to multi-stage carburetors wherein the secondary stage is controlled automatically by vacuum responsive means.

Increasing horsepower of automotive internal combustion engines necessitated the use of two-stage carburetion as provided by the well-known two or four barrel carburetor in which the throttle plate (or plates) controlling the flow of fuel-air mixture through the primary barrel (or barrels) is manually operated -and the secondary throttle plate (or plates) is automatically opened against a spring tending to hold it closed by a suction device having a diaphragm actuated by primary `and/ or secondary venturi vacuum. The secondary barrels thus supplement the primary barrels when the capacity of the latter is exceeded.

In truck or other applications where it is desired to govern the speed of the engine and/or the speed of the vehicle, a second suction device actuated by primary venturi yand/or manifold vacuum is provided to override the manual operation of and to close the primary throttle plate or plates, the intensity iof the governing vacuum being controlled by a speed sensitive valve adapted to close an air bleed when the governed engine and/or vehicle speed is reached.

The -secondary throttle plates open and cl-ose in accord-ance with vacuum developed at the primary and/or secondary venturi. Since this vacuum does not change in direct proportion tio the change in position of the primary throttle plates, the secondary throttle plates do not adjust in position to follow the primary throttle plates. This is true whether or not agovernor is incorporated in the two-stage carburetion system. Where a governor is involved, the governing action has been found to be delayed as a -result of t-he automatic secondary throttle plates not closing and opening at the same time as the primary throttle plates.

It is now proposed to provide automatic means operative only during certain periods of engine operation for dampening the movement ofthe suction responsive device which controls the position of the secondary throttle valves, whether or not a governor is being used.

Other objects and advantages of the invention will become apparent when reference is made to the following description and the accompanying illustrations wherein:

FIGURE 1 is a side elevational view, with portions thereof in cross section, of a `four-barrel carburetor provided with a governor, embodying the invention;

FIGURE 2 is a side elevational view, with portions thereof in cross section, t-aken on the plane of line 2-2 of FIGURE 1 and looking in the `direction of the arrows; FIGURE 3 is ya cross sectional view tak-en on the plane of line 3-3 of FIGURE 1 and looking in the direction of the arrows;

FIGURE 4 is a bottom plan view taken on the plane of line 4-4 of FIGURE 1 and looking in the direction of the arrows; FIGURE 4 illustrates the manner in which the carburetor shown by FIGURE 1 is -cut away to illustrate the primary and secondary throttle plates.

Referring now to FIGURE 1, a four-barrel carburetor having an air intake 12 and equipped with an air cleaner 13 is cut away as shown by FIGURE 4 to expose one of the primary barrels 14 and one of the secondary ice barrels 16. The primary barrel 14 is provided with a restriction or venturi 18 and a throttle plate 20 mounted on the shaft 22 which extends through the other primary barrel in which is mounted a throttle plate identical to throttle plate 20. The secondary barrel 16 is also provided with a venturi 24 and a throttle plate 26 mounted lon the shaft 28 which extends through the other secondary barrel in which is mounted another secondary plate.

While a particular governed four-barrel carburetor is shown for purposes of illustration, it will be apparent that the invention is equally applicable to two-barrel or multistage carburetors Iand to ungoverned carburetors.

A suction device 30 commonly referred to as a governor diaphragm assembly is mounted -on the boss 32 and gasket 33 extending from the carburetor throttle body 34. The assembly 30v includes a casting or other body 36 formed to provide recesses 38 and 40. The recess 40 is covered by means of a flexible diaphragm 42 which is secured to the body 36 by means of a cover member 44 Aformed to provide ian air tight chamber 46 off which the flexible diaphragm 42 forms a wall. The -cover member may be secured =by -any suitable means such as screws 47.

As shown by FIGURES 1 and 2, the diaphragm 42 has secured to the center thereof in the conventional manner a rod 48 passing through passage S0 in the body 36 and having a laterally extending end 52 pivotally secured to the lever 54 which -is rigidly lsecured to the end 56 of the primary throttle shaft 22 extending into the chamber 38. The shaft 22 is mounted in the anti-friction bearing 39 and lthe steel and leather washers 43 and 45 to provide a seal. A tension spring 58 fixed between the adjustable pin 60 mounted in one of the holes 62 in the body 36 and the xed pin 64 secured to the lever 54 tends to hold the primary throttle plate 20 in the Vopen position. A cover plate `66 vented to the atmosphere as by means of vent 67 may be secured vby screws -63 against the gasket 70 so as to form a chamber 38.

The orifice 72 at the primary venturi 18 and the orifice 74 below the primary throttle plate 20 are connected by ymeans of the passages 76 and 78 having fixed restrictions `and 82 respectively with .the passage 84 in the body member 36 and the passage 86 in the cover member 44 vwhich lead to the chamber 46. A passage 88 connecting with passage 84 terminates in an opening in the body 36 adapted to receive a threaded fitting 90.

Located at any desired position on the engine is a governor valve assembly 92 comprising a stationary housing 94 adapted to be mounted on the engine and containing ashaft 96 driven in any suitable manner in proportion to engine or vehicle speed. Mounted for rotation with the shaft 96 is a laterally extending sleeve 98 having a spring 100 mounted within the axial passage 102 in the sleeve in any suitable manner, such as in the internally threaded member 104, so that the spring 100 is adjustable axially by means of the adjustment screw 106 which is reached by removing the access screw 108. The other end of the spring 100 is secured to the governor weight 110 movable axially within the chamber 112 against the spring 100 and having at the free end thereof a valve 114 adapted to close the orifice 116 when the weight 110 is forced outwardly due to the rotation of the shaft 96 and the sleeve 98 in accordance with engine speed. The engine or vehicle speed at which the orifice 116 will be closed is dependent, `of course, upon the adjustment of the spring 100. It is apparent, also, that some other governor valve structure may be employed.

Conduit 118 between the air intake 12 of the carburetor 10 and the housing 94 and conduit 122 between the housing 94 and the passage 88 in the body 36 are provided so that when the engine or vehicle is operating 4at a speed not suiiicient to close the orifice 116, engine vacuum will draw clean air through the -conduit 118, into the housing 94, through the orifice 116 and into the chamber 112, through the passage 102 and the axial passage 120 in the shaft 96 and thence through the conduit 122 to the governor diaphragm assembly 30. When the engine reaches governed speed, the orifice 116 is closed and the air bleed through conduit 122 is cut o. Vhen this occurs, vacuum in the chamber 46 urges the diaphragm 42 downwardly, as in FIGURE 2, against the spring 5S to close the primary throttle plates 20.

A secondary throttle diaphragm assembly 124 is mounted at the yopposite side of the throttle body 34. This assembly comprises a body 126 having a recess 128 closed to the atmosphere by a plate 130 secured by screws 132 and a recess 134 closed by a flexible diaphragm 136 which is secured to the body 126 by means of a cover 138 formed to provide oppositely disposed chambers 140 and 142 between which the flexible diaphragm 136 forms a movable wall. The chamber 142 contains a compression spring 144 positioned between the cover 138 and the rod 146, which is secured to the center of the diaphragm 136, so that the spring 144 urges the rod 146 upwardly to rotate the lever 148 secured rigidly to the secondary throttle shaft 28 counterclockwise, as in FIGURE 3, and close the secondary throttle plates 26. A conduit 150 extending between the chamber 142 and the vacuum passages 152 and 154 opening to the primary and secondary venturis 1S and 24 enables primary and/or secondary venturi vacuum to evacuate the chamber 142 and displace the diaphragm 136 downwardly, as in FIGURE 1, against the spring 144 to open the secondary throttle 26. The force of the spring 144 is selected so that the secondary throttle plate 26 will be open at any predetermined venturi vacuum.

The structure `described above, or its equivalent, is well known in the art, and proper governing action is known to depend upon the particular degree of closing of the throttle plates 20 and 26 when the engine or vehicle has reached a predetermined speed. Unless the flow of motive fluid to the engine is cut off by the secondary throttle plates, hunting will occur, since the primary throttle plates have to rst close farther than would otherwise be required, in order to compensate for the open secondary plates, and then open when the secondary plates finally close.

Additionally, it is desirable that the secondary throttle plate (or plates) close at substantially the same time as the primary throttle plate (or plates) even when the governor is not included in a two-stage carburetion system. In other words, when the accelerator pedal is released, it is important for safety reasons that the plates close quickly to cut oil" the ow of motive fluid to the engine.

A further undesirable feature inherent in the two-stage operation is a condition of fluttering of the secondary throttle plate, resulting in a non-uniform rate of closing. This could be due to the action of the diaphragm 136 when the increased pressure at the primary and secondary venturis 18 and 24 is transferred to the chamber 142 via -conduit 150 and branch passages 152 and 154, once the primary throttle plates 20 close. The diaphragm initially surges upwardly, increasing the volume of the chamber 142 which isnt instantly filled by air from the vent. The instantaneous resulting greater pressure in the now smaller chamber 140 thus reacts against the diaphragm 136 to force it in the direction of least resistance, namely, downwardly, until suffi-cient additional vent air enters the chamber 142 through the relatively long conduit 150 to once again cause the diaphragm 136 to move upwardly. The secondary throttle plate 26 is, of course, following the movement of the diaphragm 136 by virtue of its direct connection thereto through the rod 146, the lever 148 and the throttle shaft 28.

It is for the above reasons, that additional means is required to close the secondary throttle plates at substantially the same time as the primary throttle plates. The specific invention embodied herein consists of means for supplying clean air to the chamber of the secondary throttle diaphragm assembly 124, along with an additional means for modulating the clean iair with engine manifold vacuum. A conduit 158 including a restriction communicates between the air cleaner and the charnber 128. A second conduit 156 communicates between the chamber 140 and the primary induction passage at a port 168 located below the primary throttle plate 20. Included in the conduit 156 is a valve seat 162, a ball check valve 164, and a spring 166 biasing the ball check 164 against the seat 162.

As long as the primary throttle valve 20 is in a wide open throttle condition, the resultant high manifold pressure causes the ball check 164 to remain against the valve seat 162, maintaining atmospheric pressure in the chamber 140 `by Virtue of the conduit 158 and the restriction 160.

Once the primary throttle plate is closed, either by the operator releasing the accelerator pedal, or as a result of the closing of theorice 116 in the governor valve assembly 92 when a governor is employed, manifold pressure below the primary throttle plate 24B in the induction'passage 14, of course, decreases. Upon reaching a predetermined value, depending upon the size of the spring 166 selected, the ball check 164 will become unseated. Thus, pressure in the chamber 140 is decreased, being influenced by the access to the low pressure in the induction passage 14 via the conduit 156. This result, in effect, aids the spring 144 to more readily move the diaphragm 136 upwardly, because of the decreased pressure ydifferential between the two chambers 140 and 142. It is apparent, therefore, that the secondary throttle plate 26 will more nearly close at substantially the same time as the primary throttle plate 20 and that the possibility of its uttering while closing will be lessened considerably.

It is important that the restriction 160 be calibrated relative to the action of the ball valve 164 and the spring 166 in order that the desired pressure drop in the chamber 140 may be attained and further in order that an excessive vacuum in the chamber 140 is not possible, the latter eliminating the possibility of diaphragm 136 rupture or jamming of the secondary throttle plate 26.

While only one embodiment of the invention has been disclosed, it is conceivable that other modifications are possible within the scope of the appended claims.

What I claim-as my invention is:

1. In an internal combustion engine, a primary intake passage having a throttle valve for controlling the iiow of motive fluid therethrough, a secondary intake passage having a throttle valve therein, resilient means for normally holding said secondary throttle valve closed, a two-way suction device actuated on one side by vacuum resulting from iiow of air through at least one of said intake passages for opening said secondary throttle valve against said resilient means, and conduit means, communicating between the other side of said two-Way suction device and said primary intake passage posterior to said primary throttle valve, said conduit including a valve actuated in response to the vacuum in said primary intake passage for at times introducing engine manifold vacuum to said suction device. v

2. A fuel control for an internal combustion engine, comprising primary and secondary intake passages each having a venturi, primary and secondary throttle valves in said intake passages for controlling the iiow of motive uid to said engine, resilient means for normally closing said secondary throttle valve in said secondary intake passage, first expansible chamber motor means responsive to venturi vacuum acting on one side thereof for opening said secondary throttle valve against said resilient means, speed responsive means and second expansible chamber motor means actuated by primary venturi vacuum and engine manifold vacuum in response to said speed respon- 5 sive means for closing said primary throttle valve when References Cited by the Examiner said speed reaches governed speed, an air bleed to the UNITED STATES PATENTS other side of said first motor means for opposing said 2 313 258 3/1943 O1 261 23 1 resilient means which is located in said one side of said 8.0m

2,823,020 2/1958 Smlth 123-127 irst vacuum responsive motor means and condult means 5 2,990,821 7/1961 Cramer 12B-103 commumcatmg between said other s1de of said first vacu- 2 991 053 7/1961 Cramer 261 23 1 um responsive motor means and said primary intake passage posterior to said primary throttle valve, said MARK NEWMAN, primary Exam-eh conduit containing a valve for at times introducing manifold vacuum for modulating the fresh air opposing said 10 FRED E' ENGELTHALER Examiner' resilient means. A. L. SMITH, Assistant Examiner. 

1. IN AN INTERNAL COMBUSTION ENGINE, A PRIMARY INTAKE PASSAGE HAVING A THROTTLE VALVE CONTROLLING THE FLOW OF MOTIVE FLUID THERETHROUGH, A SECONDARY INTAKE PASSAGE HAVING A THROTTLE VALVE THEREIN, RESILIENT MEANS FOR NORMALLY HOLDING SAID SECONDARY THROTTLE VALVE CLOSED, A TWO-WAY SUCTION DEVICE ACTUATED ON ONE SIDE BY VACUUM RESULTING FROM FLOW OF AIR THROUGH AT LEAST ONE OF SAID INTAKE PASSAGES FOR OPENING SAID SECONDARY THROTTLE VALVE AGAINST SAID RESILIENT MEANS, AND CONDUIT MEANS COMMUNICATING BETWEEN THE OTHER SIDE OF SAID TWO-WAY SUCTION DEVICE AND SAID PRIMARY INTAKE PASSAGE POSTERIOR TO SAID PRIMARY THROTTLE VALVE, SAID CONDUIT INCLUDING A VALVE ACTUATED IN RESPONSE TO THE VACUUM IN SAID PRIMARY INTAKE PASSAGE FOR AT TIMES INTRODUCING ENGINE MANIFOLD VACUUM TO SAID SUCTION DEVICE. 